A series of N-N-di-substituted analogs of dopamine found to be active as dopamine vascular receptor agonists; the benzamide, sulpiride, was found to be an extraordinarily potent and selective vascular dopamine antagonist; hemodynamic studies of N-N-di-n-propyl dopamine indicated that this agent decreases blood pressure without inducing reflex tachycardia and caused significant increases in renal, mesenteric, and femoral blood flow; sodium nitroprusside and phentolamine were found to be effective in antagonizing the vasoconstriction produced by dopamine in the intact dog. Dopamine containing fibers were located in the glomerular vascular poles of the canine kidney. The prostaglandin antagonist, 7-oxo-prostynoic acid, was found to have greater effect on the vasoconstriction produced by PGE2 and PGF2a in isolated canine and rabbit arterial strips. Insulin plays an important role in the culture of hepatocytes. N-demethylation of antipyrine by a breath test is a sensitive indicator of lever disease.